Posted: 04/04/2017 at 14:22
N.P.K. it will be on the side of the box or bag of any make name or brand of fertiliser you buy and makes up 95% of the plants needs in varying amounts of the N.P.K. Nitrogen for green growth, Phosphorus for general health and Potassium for ripening fruit or flowering. The other five percent is made up of trace elements including iron sulphur calcium and magnesium plus many more infinitely smaller traces of many substances found in the ground they are grown in. In other words almost exactly the same we as humans need to exist and also overfeed them they will either die or become blowsy and listless. Lack of certain minerals caused crops to be small or fail though people learnt the hard way certain chemicals were needed at certain times, nothing mysterious just good old nous and experiment and then handed on.
These facts have been know since the first gardens came into existence and carried on from Father to Son or Daughter, natural animal fertiliser from the midden held those minerals remembering that even in my time human waste was often added to the midden. In time the soil is leached of those minerals hence the big effort in 1914 to start making organic fertilisers so more food could be grown on the same amount of land.
ICI came into being in 1926 and I worked for them (not that early of course) seeing what went into the Fertiliser asking the Labs why certain things were added or not. Being a maintenance group we saw it all and products being made up and bagged for almost every fertiliser brand in the Country and even abroad all coming out of the same particular mix, Lush lawns Nitrogen heavy, Tomato's Potassium heavy. The rest down to trial and error from a multitude of Farmers gardeners and General plant growers. Having seen some of the very obvious mistakes that so called Scientific experts have made in recent times I would treat their word with caution.